Your understanding is the same as mine (/dev/shm = AMM). With my customers, I set the USE_LARGE_PAGES parameter to ONLY when configuring hugepages. I would be interested to know if this makes any difference in your situation, if you haven't already set it. Admittedly, I haven't checked /dev/shm allocations the way you did after configuring hugepages; I'll check this when I have a chance and let you know what I see. http://docs.oracle.com/cd/E16655_01/server.121/e17615/refrn10320.htm#REFRN10320 -Justin On Wed, Apr 16, 2014 at 12:19 PM, Mark Bobak <Mark.Bobak@xxxxxxxxxxxx>wrote: > Hi Mike, > > AMM (Automatic Memory Management), which is setting memory_target and > letting Oracle manage both SGA and PGA from that chunk of memory, is only > available in 11g, and *not* compatible with hugepages. > ASMM (Automatic Shared Memory Mangement), which is setting sga_target and > pga_aggregate_target, is available in 10g, and is compatible with hugepages. > > My understanding was that /dev/shm segments and hugepages were mutually > exclusive...but perhaps not? > > Anyhow, I'm seeing ASMM + hugepages + segments in /dev/shm, which I > thought wasn't possible. > > -Mark > > From: <Cunningham>, Mike <mcunningham@xxxxxxxxxxxxxx> > Date: Wednesday, April 16, 2014 at 1:13 PM > To: "Chris.Ruel@xxxxxxx" <Chris.Ruel@xxxxxxx>, Mark Bobak < > Mark.Bobak@xxxxxxxxxxxx>, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx > > > > Subject: RE: Question about hugepages, shared memory, and /dev/shm.... > > For what it's worth. While using AMM with huge pages the instance in > my environment crashed on occasion during memory resizing. That was on > version 10.2.0.3 with Linux 5.7 (x86_64). > > > > I did not pay attention to the /dev/shm so I can't offer anything there. > Also, learning from my past errors, I have never tried AMM in 11g with huge > pages. > > > > *Michael Cunningham* > *Senior Database Administrator* > *The Doctors' Company* > 707.226.0221 - desk > 707.337.0184 - cell > > > > *From:* oracle-l-bounce@xxxxxxxxxxxxx [ > mailto:oracle-l-bounce@xxxxxxxxxxxxx <oracle-l-bounce@xxxxxxxxxxxxx>] *On > Behalf Of *Ruel, Chris > *Sent:* Wednesday, April 16, 2014 8:59 AM > *To:* Mark.Bobak@xxxxxxxxxxxx; oracle-l@xxxxxxxxxxxxx > *Subject:* RE: Question about hugepages, shared memory, and /dev/shm.... > > > > I don't know if you have come across this MOS doc yet but it's pretty good > at explaining some things relating to HP's: > > > > Oracle Support Document 361323.1 (HugePages on Linux: What It Is... and > What It Is Not...) can be found at: > https://support.oracle.com/epmos/faces/DocumentDisplay?id=361323.1 > > I would also add that depending on the version of Linux, you need to > disable Transparent Huge pages for OEL6...at least we did. Look at the > referenced documents at the bottom and there is an article on this. If you > don't disable THP's, it can cause problems in RAC environments. > > > > For your questions below, your understanding correct for #1 and #2. I * > *think** you are correct on #3 and #4 but I have not dove in that far > myself...have left it up to sysadmins to make sure it works... > > > > Chris.. > > > > > > > > > > Chris Ruel * Oracle Database Administrator > > cruel@xxxxxxx * Desk:317.759.2172 * Cell 317.523.8482 > > > > *From:*oracle-l-bounce@xxxxxxxxxxxxx > [mailto:oracle-l-bounce@xxxxxxxxxxxxx<oracle-l-bounce@xxxxxxxxxxxxx>] > *On Behalf Of *Mark Bobak > *Sent:* Wednesday, April 16, 2014 11:47 AM > *To:* oracle-l@xxxxxxxxxxxxx > *Subject:* Question about hugepages, shared memory, and /dev/shm.... > > > > Hi All, > > > > So, I thought I really understood this stuff, but I'm a little baffled > here, and I wonder if anyone can offer me a clue? > > > > Here's what I (think I) know: > > 1.) AMM (setting memory_target) is *not* compatible with a hugepages > configuration. Any attempt to use hugepages will lock out the memory > allocated to hugepages and AMM will only use non-hugepage memory > allocations, the effect of which would be like removing the huge page > allocated memory from the system. > > 2.) ASMM (setting sga_target and pga_aggregate_target) and MMM (manually > setting db_cache_size and pool sizes) *are* compatible with a hugepages > configuration, and for any non-trivially sized SGA, hugepages is strongly > recommended. > > 3.) If hugepages are *not* configured, and AMM is used, memory segments > will be mapped in /dev/shm. > > 4.) If hugepages *are* used, no memory segments will be visible in > /dev/shm. > > > > So, that's what I think is true about memory configuration and hugepages > configuration. > > > > That seems to be consistent throughout our environment, which mostly has > ASMM or MMM and hugepages configuration. > > > > However, and this is where my confusion comes in, we have several eBS > environments, which seem to have a valid and active hugepages > configuration, are using ASMM (not AMM), and *still* I can see memory > segments allocated in /dev/shm?? Any idea how this is possible? > > > > Here's an example from our preprod environment: > > (Content was too long for Oracle-L, so here's a paste bin URL) > > > > http://pastebin.com/7w2V2jEa > > > > So, I'm a little baffled here. I thought these were mutually exclusive > features. > > > > Note also that the timestamps on the /dev/shm segments is *after* instance > startup time, so, I don't think these are "orphan" memory segments.... > > > > Anyone out there can clue me in? > > > > Thanks, > > > > -Mark > > Notice of Confidentiality: **This E-mail and any of its attachments may > contain > Lincoln National Corporation proprietary information, which is privileged, > confidential, > or subject to copyright belonging to the Lincoln National Corporation > family of > companies. This E-mail is intended solely for the use of the individual or > entity to > which it is addressed. If you are not the intended recipient of this > E-mail, you are > hereby notified that any dissemination, distribution, copying, or action > taken in > relation to the contents of and attachments to this E-mail is strictly > prohibited > and may be unlawful. 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